In a file system environment, physical snapshots of the physical file system include a point-in-time state of the entire network accessible portion of the file system. Client computing devices in such a direct client-server environment can directly obtain the physical snapshots from the servers. Unlike non-virtualized file systems in which a network-accessible file resides on a single storage device accessible directly to client computing devices, in a virtualized file system, a network-accessible file system may exist on multiple storage devices, transparent to the client computing devices, and managed by a file virtualization device interposed between the client computing devices and the servers. In such virtualized file systems, a virtual snapshot that includes an aggregation of physical snapshots may exist on multiple physical storage devices, or, in some cases, on the same storage device but on different physical file systems. The aggregate of all the physical snapshots in a file virtualization device is required to provide the client computing devices with a complete view of the network-accessible file system. If one or more of the physical snapshots making up a virtual snapshot is missing, the client computing device does not get complete state of the file system via the snapshot. Generating such virtual snapshots and presenting them to requesting client computing devices is disclosed in U.S. patent application Ser. No. 12/334,281, filed Dec. 12, 2008, entitled “Methods for Generating a Unified Virtual Snapshot and Systems Thereof,” which is hereby incorporated by reference in its entirety.
However, in conventional file virtualization systems, if the file virtualization device experiences a catastrophic failure and a complete reconfiguration is required, no technology exists that enables the file virtualization device to “re-learn” all the snapshots managed prior to the catastrophic failure. Further, the file virtualization device does not have knowledge of translating the physical snapshots into a coherent virtual snapshot after the failure.
In another scenario, if a customer deploying the file virtualization device elects to purchase newer, faster file virtualization device, existing snapshots are difficult to be transferred to the new file virtualization device. Alternatively, if the customer wishes to split a virtual volume on a file virtualization device into two or more volumes, there is no technique or system that lets the new volumes to be automatically reflected in a new virtual snapshot that provides information about the splitting of the original volume into two or more volumes.
In yet another scenario, if a customer is using file server based replication for data and file virtualization device clusters are front-ending both primary and disaster recovery (or, backup) sites, conventional file virtualization systems fail to efficiently make the replicated snapshots available to client computing devices from the backup site file virtualization device.
The above problems are further intensified if the customer has many years of snapshots that need to be managed. Further, the virtual snapshot itself is not shared with a backup recovery site, which makes it very difficult to recover the state of the file system in the event of a disaster. Using conventional file virtualization devices, usually such recovery, if at all possible, is a time consuming and tedious manual operation highly prone to errors. Furthermore, using current file virtualization devices, maintaining the virtual snapshots while at the same time performing operations such as reconfiguring a file switch, upgrading, renaming, mounting and/or unmounting a new volume, coalescing multiple volumes into a lesser number of volumes, splitting one volume into a plurality of volumes, preventing accidental removal of snapshot rules, and sharing snapshots between two or more file switches or file virtualization devices is complex, time consuming, and error prone. Unfortunately, current file virtualization systems fail to address the above-noted and other problems associated with virtual snapshots.